This invention relates to addition polymerizable adducts, to their use in the stabilization of nonaqueous dispersions and to urethane polymers prepared using such dispersions.
Polyurethanes constitute a broad class of polymeric materials having a wide range of physical characteristics. The polymers are produced by the reaction of a polyisocyanate with a polyfunctional compound having an active hydrogen in its structure. This active hydrogen compound is generally a liquid or solid capable of being melted at relatively low temperatures. Most commonly, the active hydrogen compound contains hydroxyl groups as the moieties having the active hydrogen and thus are termed polyols, e.g., the polyols of polyesters, polyester amides, or polyethers, or mixtures of two or more such materials. For reasons of commercial availability and cost, the polyols most commonly employed in the preparation of polyurethanes are the polyethers having hydroxyl terminated chains and hydroxyl terminated polyesters.
Although a wide variety of physical and chemical properties are obtainable by the proper selection of a polyisocyanate and the polyol as well as the conditions under which the polyurethane reaction is carried out, the resulting polyurethane often exhibits properties, e.g., load bearing and processability, which are unacceptable for some applications, particularly for foam applications as well as for elastomer and plastic applications.
To improve such properties, it has been the practice of the art to employ graft copolymer dispersions (often called polymer polyols) prepared from vinyl monomers and polyols in the preparation of polyurethanes, e.g., as shown in U.S. Pat. Nos. 3,383,351; 3,304,273; 3,523,093; 3,652,639 and 3,823,201. In 3,304,273, a mixture of styrene and a polar monomer are copolymerized while dispersed in a polyol which is essentially free of ethylenic unsaturation. Unfortunately, stable dispersions cannot be prepared by this technique if high proportions of styrene monomer are employed. Subsequently, in order to overcome this problem, it was found desirable to employ polyols which contain a significant amount of ethylenic unsaturation. For example, as stated in U.S. Pat. No. 3,823,201 to Pizzini et al.,
" . . . the stability of dispersions obtained by the in situ polymerization of vinyl monomers in polyols is a result of the formation of surface stabilizing species. Without a stabilizing species which provides a repulsive barrier between the polymer particles, the polymerized material will agglomerate and form irregularly shaped lumps. . . . the stabilizer is an amphipathic polymer consisting of lyophobic vinyl polymer and lyophilic polyether chains. The vinyl polymer part is absorbed and/or chemically built in the particle surface while the polyether part reaches out in the surrounding polyol phase providing a protective shield against coagulation." PA1 (A) a polyahl (as defined hereinafter) having dispersed therein, PA1 (B) an addition copolymerizate of (1) the aforementioned adduct and (2) at least one ethylenically unsaturated monomer; or PA1 (C) the reaction product of (1) a copolymer of an unsaturated heteroatomic monomer and at least one other ethylenically unsaturated monomer and (2) a monoahl (as defined hereinafter), a polyahl or mixture of monoahl and polyahl; or PA1 (D) a combination of (B) and (C); or PA1 (E) a combination of (B) and/or (C) and a polymer of at least one "other monomer", said copolymerizate and/or reaction product being present in an amount sufficient to stabilize the dispersion.
Although it is desirable to have some unsaturation in the polyol, it has been found (e.g., U.S. Pat. No. 3,651,639 to Pizzini et al.) that larger mole ratios of unsaturation to polyol such as 1:1 to 3:1 cause unacceptably high viscosities in the resultant dispersions.
Accordingly, it is highly desirable to provide a nonaqueous copolymer dispersion exhibiting increased stability and reduced viscosities.